Human herpesvirus 8 (HHV-8): HHV-8 DNA sequences were found in spindle cells, rather than stromal areas, of Kaposi's sarcoma (KS). It also was more common in peripheral blood mononuclear cells of KS patients compared to other HIV-infected persons. Prevalence in Africans and U.S. pregnant women and infants and, particularly, incident reactivity in VEB's cohort of homosexual men and its the relationship to incident KS are being examined with an HHV-8 immunofluorescence assay. Efforts to develop other serologic tests are underway. Epstein-Barr virus (EBV): Methylation of the EBV C promoter was found in African Burkitt's lymphoma and Hodgkin's disease tumors, revealing a method by which these EBV-associated malignancies avoid cytotoxic T-cell immune surveillance. Human Papillomaviruses (HPV): With several methods of DNA detection and serology, prostate cancer was shown not to be associated with HPV, refuting some recent claims. HPV 45 is rare in the U.S. but was found commonly in cervical neoplasia in Jamaica, consistent with recent findings that HPV 45 is an important cause of cervical cancer in women of African decent. Antibodies to HPV 16 were shown to distinguish patients with cervical neoplasia from normal controls. Good interlaboratory concordance was found with an HPV 16 virus-like particle ELISA. This antibody assay was applied to a serosurvey of 905 cancer patients, finding that HPV 16 positivity was high with several genital tumors (cervix, vulva, vagina, and penis) but not with other epithelial tumors. Simian Virus 40 (SV40): In contrast to recent reports, SV40 DNA was not detected in mesotheliomas using a PCR with a demonstrated of 1-10 virus copies, nor did antibodies to SV40 T-antigen suggest an association of SV40 infection with mesotheliomas or osteosarcomas. Hepatitis C Virus (HCV): Substantially increased mortality due to hepatic failure was found in two populations with high HCV and HIV prevalence rates -- intravenous drug users and hemophiliacs. These studies imply that VEB's previous findings of markedly increased HCV serum levels with HIV-related immune deficiency have substantial clinical consequences.